| 摘要: | 本研究製備與改質鈀銀薄膜以應用於氫氣分離。研究中利用手填改質(manual (M-) modification method)或抽吸輔助改質法(suction-assisted (S-) modification method)將基材表面孔洞縮小並藉由多種無電鍍(electroless plating, ELP)及電鍍法(electroplating, EP)鍍覆鈀銀膜在改質後之基材上。鈀銀膜之表面形貌以及組成藉由掃描式電子顯微鏡(scanning electron microscope, SEM)配備能量散佈分析儀(energy dispersive X-ray spectroscopy, EDS)進行鑑定，並進行氫氣滲透測試。
本研究中，在M改質之基材上，藉由銀浴控制無電鍍共鍍法(Ag-controlled electroless co-plating, Ag-ELCP)製備樣品A及B，樣品C, D,及E分別藉由Ag-ELCP三次、Ag-ELCP/EP以及Ag-ELCP/ELP(Pd)方法鍍覆鈀銀膜，並以不同溫度時間熱處理。
然而，經由上述製備的程序，A-D明顯無法達到緻密的表面形貌以及最佳的組成條件(鈀/銀=77/23)。而樣品E的鈀/銀組成雖然為85/15，但是由於其在兩次的600 oC持溫3小時熱處理後，銀基材嚴重燒結導致氣體無法滲透而無法量測到氫氣與氮氣的通量。
此外藉由S-method可以得到比M-method更為均勻之改質層並且利用逐層析鍍法(ELP(PdAg)/EP)可以製備出更厚的膜，且由於膜增厚所需熱處理溫度必須提高並增加熱處理時間，因此樣品M1以及S2的熱處理條件從350 oC提升至600 oC 持溫5小時，兩者均具有氮氣氣密性。M1和S2 在100 oC，而氫氣通量在壓差為4 atm時分別為0.5以及1.1 (mole-m-2-s-1)，其速率決定步驟分別為混合控制反應以及表面控制反應。
在水氣(H2O(g))的影響下，M1和S2之氫氣通量在壓差為4 atm時分別降低至0.3和1.0 (mole-m-2-s-1)，相對地減少了40以及9 %的氫氣通量，且因為水氣與氫氣的競爭效應關係，兩者之速率決定步驟皆為表面控制步驟。;Herein, the preparation and modification of PdAg membrane used for H2 separation has been studied. Two kinds of surface modifications, manual (M-) or suction-assisted (S-) methods are used to reduce the pore size of the substrate and the PdAg membranes are then deposited on the modified substrates by different cycles of electroless plating (ELP) and electroplating (EP) processes. The morphology and composition of the as-prepared composite membranes are characterized by scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and applied for H2 permeation.
The Ag-controlled electroless co-plating (Ag-ELCP) are used to prepare samples A and B on M-substrate and samples C, D, and E are prepared by three times of Ag-ELCP, Ag-ELCP/EP, and Ag-ELCP/ELP (Pd), respectively, with different heat treatments. However, it seems that the membranes (A-D) cannot reach dense morphology and the optimal Pd/Ag ratio of 77/23. On the other hand, the sample E has a Pd/Ag composition of 85/15 but the substrate has been severely sintered after two-cycle heat treatment at 600 oC for 3 hrs.
By using sequential plating process (ELP(PdAg)/EP) and S-modification, the thicker membrane can be fabricated and the heat treatment at temperature of 600 oC for a longer time is necessary than M-method. Therefore, both M1 and S2 are treated at 600 oC for 5 hrs. Both membranes can reach the gas tight level. The JH2 of M1 and S2 is about 0.5 and 1.1 (mole-m-2-s-1) under pressure difference of 4 atm and the permeation behavior of M1 and S2 is the mixed controlled process and surface adsorption controlled process, respectively.
In terms of the H2O(g) effect on the H2 permeation, the JH2 with H2O(g) are 0.3 and 1.0 (mole-m-2-s-1) for M1 and S2, when applied pressure difference of 4 atm and the depletion ratio is 40 and 9 %, respectively. The controlling process is mass transfer for both M1 and S2 samples, resulting from the competition effect of H2 and H2O(g). |
